Sintering compacts and forms a solid mass of material by heat or pressure without melting it to the point where it liquifies. Depending on the following factors, sintered thermoplastics will have both artificial pores and large natural pores of varying size:

Size distribution of the plastic powder particles

Compacting pressure

Amount of heat applied

Amount of time during which heat and pressure have been applied

Typical pore sizes range from about 5 microns to 350 microns. Typical void volumes range from 30% to 50%, but can be produced with up to 70% . Pore size and void volume affect how well a porous thermoplastic media will vent, diffuse, filter, or serve as a type of barrier protection. Additionally, pore size and void volume will affect how permeable that media will be to air, and how water resistant or waterproof that material will be in different environments.